1. Field of the Invention
This invention relates generally to pneumatic and hydraulic equipment, and more particularly to the measurement of physical characteristics, such as flow rate, pressure, and temperature of a fluid used to control these devices.
2. Description of the Prior Art
A fluid flow device, such as a valve manifold 10 and its corresponding base plate 12 shown in FIG. 1, is used to accurately direct fluids used to control pneumatic and/or hydraulic equipment. Fluid flow devices and other control devices are disclosed in U.S. Pat. No. 5,348,047 to Stoll, et al. and U.S. Pat. No. 5,458,048 to Hohner, which are incorporated herein by reference. The term xe2x80x9cfluidxe2x80x9d is generically used herein to refer to any gas, liquid, suspension, and/or slurry used as a control medium in such equipment.
The base plate 12 is mounted to a bottom surface of the valve manifold 10, as shown by dashed lines in FIG. 1. The base plate 12 includes channels 16, which pass through the base plate 12 and coincide with apertures on the underside of the fluid flow device 10. A fitting 14 is fitted to one end of each of the channels 16. The fittings 14 can readily be connected to tubes that direct the fluid to and/or from the valve manifold 10. The channels 16 then direct the fluid through the base plate 12 to the appropriate aperture in the valve manifold 10. The valve manifold 10 can then redirect or modify the flow of fluid in response to electronic control.
In addition to directing the flow of fluid, another function that may be performed is the measurement of fluid characteristics, such as flow rate, pressure, and temperature. One type of sensor 18, which is used to measure the flow of liquid, is shown in FIGS. 2a, 2b, and 2c. The flow sensor 18 includes an orifice 20, a cantilever paddle structure 22, and an implanted piezo-resistive Wheatstone bridge 24. FIG. 2a shows the paddle structure 22 in an undeflected state, and FIG. 2b shows the paddle structure 22 in a deflected state.
The fluid to be measured is directed through the orifice 20 in the flow sensor 18. The dynamic pressure built up by the fluid deflects the paddle structure 22. The mechanical stress of the paddle structure 22 changes the resistance of the piezo-resistive Wheatstone bridge 24 at the base of the paddle structure 22, and this change in resistance creates a corresponding change in voltage. The change in voltage is detected on a set of contacts 26 electrically connected to the Wheatstone bridge 24, as shown in FIG. 2c. For temperature compensation, a second Wheatstone bridge is preferably positioned on the flow sensor 18 surrounding the orifice 20. A support member preferably positions the paddle structure 22. The size of the support member is preferably minimized to concentrate the mechanical stress of deflection, and thus increase the sensitivity of the flow sensor 18. Furthermore, the overall size of the flow sensor is determined by the paddle size, which can be adjusted to the specific needs of the control task.
The output voltage of the Wheatstone bridge 24 is proportional to the square of the volumetric flow rate. The sensitivity of the flow sensor 18 is dependent upon the size of the orifice 20, and is adjustable over a broad range. Thus, since the paddle structure 22 is perpendicularly oriented to the direction of flow of liquid, as liquid passes through the orifice 20 in the flow sensor 18, the kinetic pressure of the liquid induces a mechanical stress that is detected by the piezo-resistors in the Wheatstone bridge 24.
To incorporate the flow sensor shown in FIGS. 2a, 2b, and 2c in conventional fluid flow devices, additional tubing, fittings, and connectors must be spliced into the network of tubes coupling the base plate 12 to and from the source of the fluid and portions of the equipment to be controlled. The additional tubes, fittings, and connectors increase measurement error, space requirements, and the cost of installing and maintaining the equipment. In addition, the electronics that monitor the sensors require a substantial amount of additional wiring, which adds to the clutter of the resulting system and severely degrades its reliability. Further, the sensors and associated electronics, by being externally located to the fluid flow device, are inherently unprotected from environmental hazards, such as shock, dust, and pollutants, which are common in and around hydraulic and/or pneumatic equipment.
It is an object of the present invention to provide an integrated fluid sensing device, which significantly reduces measurement errors, space requirements, and the cost of installing and maintaining sensors that measure the physical characteristics of a fluid used to control hydraulic or pneumatic equipment.
It is a further object of the present invention to provide an integrated fluid sensing device, which includes sensors mounted on a single circuit board having common signal processing, communication, error control, and connecting circuitry.
It is still a further object of the present invention to provide an integrated fluid lo sensing device, which can readily be adapted to various physical characteristics of a fluid used to control hydraulic or pneumatic equipment by changing a single circuit board.
It is yet a further object of the present invention to provide an integrated fluid sensing device, which can readily display and transmit sensed data, via wired or wireless means, which represents physical characteristics of a fluid used to control hydraulic or pneumatic equipment.
It is still another object of the present invention to provide an integrated fluid sensing device that significantly reduces the amount of external tubing, connectors, and fittings required to sense the physical characteristics of a fluid used in the control of hydraulic or pneumatic equipment.
It is yet another object of the present invention to provide an integrated fluid sensing device, which substantially encloses sensors that measure the physical characteristics of a fluid and protects these sensors against environmental hazards.
In accordance with the present invention, an integrated fluid sensing device is provided, which includes a fluid flow device and a circuit board. The fluid flow device includes a first mating portion and a second mating portion. The first mating portion includes a first aperture, and the second mating portion includes a second aperture. The first aperture and the second aperture are at least partially aligned such that the first aperture and the second aperture define a first channel through the first and second mating portions when the first and second mating portions are joined together. The first channel is able to communicate fluid therethrough. The circuit board is disposed between the first mating portion and the second mating portion and includes at least one sensor. The sensor is at least partially aligned with the first channel and is able to detect a physical characteristic of the fluid flowing through the first channel.
In further accordance with the present invention, a method of integrating a sensor in a fluid flow device is provided, which includes the steps of dividing the fluid flow device into a first mating portion and a second mating portion, and positioning a circuit board between the first mating portion and the second mating portion. The first mating portion including a first aperture, and the second mating portion including a second aperture. The first aperture and the second aperture are at least partially aligned such that the first aperture and the second aperture define a first channel through the first and second portions when the first and second mating portions are joined together. The first channel is able to communicate a fluid therethrough. The circuit board includes at least one sensor, which is at least partially aligned with the first channel. The sensor is able to detect a physical characteristic of the fluid flowing through the first channel.
In still further accordance with the present invention an integrated fluid sensing device is provided, which includes at least one valve, a base plate, and a circuit board. The base plate is removably coupled to the valve and includes a first mating portion and a second mating portion. The base plate includes a first channel through the first and second mating portions when the first and second mating portions are joined together. The circuit board is disposed between the first mating portion and the second mating portion The circuit board includes at least one sensor and an electrical contact. The electrical contact is coupled to the sensor and is accessible to an exterior of the fluid flow device when the first and second portions are joined together. The sensor is at least partially aligned with the first channel and is able to detect a physical characteristic of the fluid flowing through the first channel.
These and other objects, features, and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.